JPH10140220A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which restrains powdering of coke and aggravation of aeration in a furnace caused by the powdering of coke and can release the limitation of coke quality by efficiently acting powdery carbonaceous material blown from a tuyere as a reducing agent. SOLUTION: An operational method of a blast furnace blows the powdery carbonaceous material together with N2 (carrier gas) into the furnace by using a lance 2 for blowing the powdery carbonaceous material, fitted to in the tuyere 1 so as to satisfy the (1)-(3) conditions. The (a) in the figure is a plane containing the tip part of the lance 2 for blowing the powdery carbonaceous material and the center axis 3 of the tuyere and the (b) is the figure vertically projecting the tip part of the lance in the vertical plane to the center axis of the tuyere containing the tip part of the tuyere 1. (1) 0.5×Rt <Rb , (2) -45 deg.C<=θ<=+45 deg.. (3) 45 deg.<=ϕ. Wherein, Rt is the inner diameter of the tuyere, Rb is the distance between the projected image center of the tip part of the lance and the center axis of the tuyere, θ is the angle of the straight line connecting the projected point of the tip part of the lance with the center of the tuyere to the vertical upward direction (reference) and ϕ is the angle of the straight line connecting the center of the tip part of the lance with the upper side tip end part to the frontward direction of the center axis of the tuyere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of operating a blast furnace using pulverized carbonaceous material.

[0002]

2. Description of the Related Art In recent years, in the blast furnace operation, an operation of blowing a large amount of pulverized carbonaceous material has been aimed at, but the aim is to replace the thermal and chemical role of coke in the furnace with the pulverized carbonaceous material. The aim is to reduce the cost of pig iron by replacing part of the required coke with powdered carbonaceous material. In other words, in the blast furnace operation, coke produced iron oxide directly or by gasification of coke by the role of fuel as a fuel that generates heat by combustion reaction with hot air from the tuyere, and by the carbon (C) of the coke itself. CO
Has a role as a reducing agent to indirectly reduce via the.

Conventionally, the injection of powdered carbonaceous material into a blast furnace basically serves as a fuel, and is performed in a tuyere combustion zone (hereinafter referred to as a raceway) of the powdered carbonaceous material. Various techniques have been developed to increase the combustion efficiency of coal.

For example, Japanese Patent Publication No. Sho 60-53082 discloses that when a powder fuel is blown from a burner which penetrates and penetrates a wall of a blowpipe for hot air blowing provided at a tuyere of a blast furnace. A method is disclosed in which the tip of the burner is set at a predetermined position with respect to the inner peripheral surface of the outlet end of the blow pipe and the blow is performed. A blast furnace blowing device for powdered fuel, which has a limitation such as setting the [major axis length / minor axis length] ratio within a range of 1.3 to 3.5, has been proposed. Japanese Patent Application Laid-Open No. Hei 6-330113 discloses a method in which a plurality of lances for injecting solid fuel are arranged at a position where the center axis of their leading ends does not intersect with the center axis of the blow pipe to perform blowing. Have been.

[0005] However, the operation of blowing the pulverized carbonaceous material into the blast furnace has a great effect on the condition inside the furnace, particularly the condition inside the coke to be replaced. That is, when the coke charged from the furnace top descends to the vicinity of the middle stage of the furnace, it reacts with CO ₂ or H ₂ O generated by the reduction of the ore (so-called direct reduction reaction), and thereby the coke strength (thereby increasing the particle size). Is maintained). After that, the coke descends to the lower part of the furnace and burns and disappears as fuel on the raceway. In conjunction with this, coke powdering proceeds simultaneously on the raceway. Therefore, when the degree of pulverization becomes remarkable as compared with the reaction quenching rate of coke, deterioration of the in-furnace air permeability due to the generated powder comes to the surface. Furthermore, when the pulverized carbonaceous material is blown, the pulverized carbonaceous material is burnt and gasified, so that the reaction quenching speed of the coke on the raceway decreases, and the amount of coke powder generated on the raceway increases. become.

[0006] In the operation of blowing the pulverized carbonaceous material into the blast furnace, the air permeability in the furnace inevitably decreases with a decrease in the coke ratio. In addition, if the above-mentioned phenomenon becomes remarkable, the operation becomes stable. It is difficult to maintain.

At present, the pulverized coal ratio is 200 kg / t (pig iron).
In many blast furnaces, some measures have been taken to increase the coke strength in order to increase to the level, but this will offset the cost and benefits of pulverized carbonaceous material injection .

[0008] The deterioration of the gas permeability in the furnace caused by the coke pulverization behavior due to the injection of the pulverized carbonaceous material as described above is caused by the deterioration of the strength (reaction deterioration) of the coke described above due to the reaction with CO ₂ and H ₂ O. Can be eliminated by suppressing the decrease in the rate of coke reaction disappearance on the raceway.

For this purpose, it is conceivable to make the powdery carbon material blown into the furnace play a role not as a fuel but as a reducing agent. That is, since the role of the coke as a reducing agent is replaced by the powdered carbonaceous material, the reaction of the coke with CO ₂ or H ₂ O is suppressed, and the deterioration of the coke strength is suppressed.

[0010] Based on such a concept, the present inventors have proposed a method in which powdered carbonaceous material is blown into a blast furnace and is effectively used as a reducing agent in the furnace (Japanese Patent Application No. 7-21182).
No. 5). According to this method, the strength of the coke does not decrease, and it is possible to use coke of lower quality than before. However, when implementing this method, as a specific means, blowing into the furnace of powdery carbonaceous material using a nozzle penetrating into the furnace from the outer wall of the furnace wall above the tuyere,
Providing such equipment at each tuyere of an actual blast furnace having dozens of tuyeres is not always advantageous in terms of cost and maintenance.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and does not require a new facility, and is based on the premise that powdery carbonaceous material is blown from an existing tuyere.
It is an object of the present invention to provide a method for operating a blast furnace, which can prevent the coke from being pulverized and the deterioration of the in-furnace air permeability caused thereby.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed that the above-mentioned powdery carbon material is effectively used (consumed) as a reducing agent instead of as a fuel in a furnace. We repeated our study based on this concept. As a result, by setting the tip of the pulverized carbonaceous material injection lance at a predetermined position at the tuyere tip, and blowing the pulverized carbonaceous material together with the carrier gas, it is possible to effectively use the pulverized carbonaceous material as a reducing agent. confirmed.

That is, the hot air blown from the tuyere is
After forming a raceway by giving a turning motion to the coke, it turns into an upward flow, but by properly adjusting the position where the powdery carbon material is put on the gas flow passing through the tuyere,
The residence time of the pulverized carbonaceous material in the raceway can be minimized, and the pulverized carbonaceous material can be quickly put on the upward flow.

The present invention is characterized in that such a pulverized carbonaceous material is blown, and its gist lies in the following method of operating a blast furnace.

Using a powdery carbonaceous material blowing lance mounted in the tuyere so as to satisfy the following conditions (1) to (3), the powdery carbonaceous material is blown into the furnace together with nitrogen gas. Characteristic blast furnace operating method.

(1) The projection point of the tip of the lance perpendicular to the plane, including the tip of the tuyere and perpendicular to the center axis of the tuyere, satisfies the following equation.

0.5 × R _t <R _b ... Where R _t : radius inside the tuyere R _b : distance between the center of the projected image of the tip of the lance and the central axis of the tuyere.

(2) In the plane described in the above (1),
The angle θ formed with respect to the vertical upward direction (reference) of the straight line connecting the projection point of the tip of the lance and the center of the tuyere satisfies the following expression.

−45 ° ≦ θ ≦ + 45 ° where the angle is + in the clockwise direction and − in the counterclockwise direction with respect to the reference.
And

(3) In a plane including the tip of the lance and the center axis of the tuyere, a straight line connecting the center of the tip of the lance and the upper tip of the tuyere is in the tuyere forward direction of the center axis of the tuyere (reference). Satisfies the following equation.

45 ° ≦ φ where the angle is an angle with respect to a reference when the tuyere front direction is set to the left in the plane.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for operating a blast furnace according to the present invention will be described in detail.

In the blast furnace, the area where carbon contained in the carbonaceous material (ie, coke or powdered carbonaceous material blown from the tuyere) is mainly consumed is the tuyere raceway and the ore located above the tuyere. This is an area where softening fusion occurs (hereinafter, referred to as a fusion zone).

In the tuyere raceway, C in the carbonaceous material is turned into combustion gas by O ₂ and H ₂ O in the blowing gas by the following reaction.

C + O ₂ → CO ₂ ; CO ₂ + C → 2CO C + H ₂ O → CO + H ₂ C + 2H ₂ O → CO ₂ + 2H ₂ ; CO ₂ + C → 2CO On the other hand, in the cohesive zone, C in the carbonaceous material is Participates in the reduction reaction and gasifies. This is so-called gasification by direct reduction. The reaction here is as follows. The process of generating CO ₂ and H ₂ O by gas reduction of the ore, and the C in the carbonaceous material reacts with the generated CO ₂ and H ₂ O to gasify. The process proceeds in parallel.

FeO + CO → Fe + CO ₂ ; CO ₂ + C → 2CO FeO + H ₂ → Fe + H ₂ O; C + H ₂ O → CO + H
_{2 In} addition to the consumption of C as described above,
There is a reaction that acts directly on FeO (ore) to reduce it, and a reaction that is consumed by carburization. In addition,
The consumption of C as a carburizing agent in such a cohesive zone is also considered herein as furnace consumption as a reducing agent.

Generally, in the operation of a blast furnace, 1 ton of pig iron
In producing on, approximately 150 kg of C is consumed as a reducing agent through the above process (including consumption as a carburizing agent as described above). At this time, in the so-called all-coke operation, coke covers all of this, but when pulverized carbonaceous material is blown into the furnace and used as fuel, the coke is reduced by the reduced coke ratio. The reaction load as an agent increases (that is, the consumption as a reducing agent per unit amount of coke increases), and as described above, the strength deterioration of coke increases.

On the other hand, considering the flow velocity of the gas rising in the blast furnace, if the carbonaceous material is a powdery carbonaceous material having a particle diameter of 0.5 mm or less, the carbonaceous material can accompany the gas flow. When the gas passes through the cohesive zone, it passes through the coke layer in a meandering manner, so to speak, the slit-shaped portion, so that the fine carbonaceous material accompanying the gas flow is captured by the ore cohesive layer. Can be

Since the powdered carbonaceous material is extremely small in size as compared with coke, in other words, has a large specific surface area and is highly reactive, the powdered carbonaceous material captured in the fusion layer consumes the above-mentioned carbonaceous material. Will be preferentially involved in the reaction being performed and will be consumed. Therefore, the reaction load of the coke is relatively reduced, and the reduction in strength due to the above-described reaction is suppressed.

In the method for operating a blast furnace of the present invention, the use of the powdered carbonaceous material lance defined as described above is performed by rapidly placing the powdery carbonaceous material blown from the tuyere into the rising airflow, This is because this powdery carbon material is effectively consumed as a reducing agent in the cohesive zone region in the furnace.

In order to determine the appropriate blowing conditions for the pulverized carbonaceous material, a coke packed bed type pulverized carbonaceous material combustion test apparatus was used.
The test was performed by changing the position of the tip of the lance for blowing the powdered carbonaceous material. This device has an internal volume of 3.5 m ³ and a bed height of 2.3.
m, depth 1.5 m, and one tuyere (inner diameter (2 × R _t ) = 65 mm) on the side wall portion 0.8 m above the bottom.

FIG. 1 is a conceptual view of a powdery carbon material blowing portion of the test apparatus, wherein (a) is a plane including the tip of the powdery carbon material blowing lance and the center axis of the tuyere, and (b). FIG. 3 is a diagram including the tip of the tuyere and projecting the tip of the lance perpendicular to this plane to a plane perpendicular to the center axis of the tuyere.

The test was carried out on seven cases in which the position of the lance for blowing the powdered carbonaceous material in the tuyere was changed by changing R _b / R _t , the angles θ and φ. Note that R _t
Is the inner radius of the tuyere 1 shown in FIG. 1 (a), and _Rb is the center of the projected point 2-1 at the tip of the powdery carbon material blowing lance 2 in FIG. 1 (b) and the center of the tuyere. 4. 1B, the angle θ is defined with respect to a vertical upward direction (reference) of a straight line connecting the center of the projection point 2-1 of the tip of the lance 2 and the center 4 of the tuyere, as shown in FIG. The angle is clockwise with respect to this reference, that is, when the projection point 2-1 at the tip of the lance 2 exists on the right side (in the state shown in the drawing), it is represented by +, and counterclockwise with respect to the reference, that is, When the projection point 2-1 at the tip of the lance 2 is on the left side-
A symbol shall be added. The angle φ is a broken line connecting the center of the tip of the lance 2 and the upper tip of the tuyere 1 on a plane including the tip of the lance 2 and the center axis 3 of the tuyere, as shown in FIG. Reference numeral 5 denotes an angle formed by the center axis 3 of the tuyere with respect to the tuyere forward direction (reference), and is an angle with respect to the tuyere forward direction (reference) when the tuyere forward direction is set to the left in the plane.

Table 1 shows the test conditions, and Table 2 shows R _b / R adjusted to change the mounting position of the lance in the tuyere.
The values of _t , angles θ and φ are shown (cases 1 to 7).

[0035]

[Table 1]

[0036]

[Table 2]

The blowing condition of the pulverized carbonaceous material was evaluated by obtaining the combustion rate of unburned pulverized coal contained in the furnace gas suctioned at a position 700 mm above the tuyere, that is, immediately above the raceway. went. The gas in the furnace was sampled three times in each case.

FIG. 2 shows the test results. The combustion rate shown is an average value of the three measurement results. Note that N ₂ / PC in the figure refers to the amount of N ₂ per kg of pulverized carbonaceous material (N
m ³ ), and the left side of the two bar graphs in each case indicates that the amount of N ₂ used as a carrier gas is 0.
3Nm ³ , and the right side is 0.7 Nm ³ .

By changing the position of the tip of the lance for blowing pulverized carbonaceous material, the burning rate of pulverized coal collected above the raceway is changed, but _Rb / _Rt is 0.5.
As described above, the angle θ is + 45 ° (30 ° and 60 °).
(Intermediate value of ゜) or less and the angle φ is 45 ° or more (the above formula) (cases 1, 2, 5 and 6), the combustion rate is 8
At 5% or less, it was lower than Cases 3, 4 and 7, which were out of this condition. Note that the angle θ is also +
The appropriate condition is -45− ≦
θ ≦ + 45 ° (the above equation).

That is, by adjusting the position of the tip of the lance for blowing the pulverized carbonaceous material so as to satisfy the requirements specified in the present invention, the residence time in the combustion zone in front of the tuyere can be shortened, and the lance can be quickly put on the updraft. It can be seen that it can be supplied to the cohesive zone as a reducing agent.

Further, when the amount of N ₂ used as a carrier when blowing the pulverized carbonaceous material is increased, the N ₂ around the pulverized carbonaceous material is increased.
An increase in the concentration (in other words, a decrease in the partial pressure of the oxidizing gas such as O ₂ , H ₂ O, etc.) and an increase in the speed at which the pulverized carbonaceous material is blown and approaching the tuyere wind speed are combined. Thus, the combustion gasification at the raceway is further suppressed. This effect is also clearly apparent under the conditions satisfying the requirements defined in the present invention.

In the present invention, N ₂ is used as the carrier gas for blowing the powdered carbonaceous material, as described above, to avoid contact of the powdered carbonaceous material with the blowing gas (particularly, O ₂ and H ₂ O). This is to suppress combustion gasification. In addition, as a carrier gas, an inert gas such as Ar can be used in addition to N ₂ .

According to the blast furnace operating method of the present invention, the carbonaceous material can be effectively used as a reducing agent by blowing the powdery carbonaceous material from the tuyere, and the pulverization due to the reaction deterioration of coke is suppressed. As a result, it is possible to suppress the deterioration of the in-furnace air permeability due to this. Therefore, when blowing the pulverized carbonaceous material, it is not necessary to take measures for increasing the coke strength, which has been conventionally adopted, and it is possible to ease the restriction on the coke quality. Also, when blowing
There is no need for new equipment such as installation of a nozzle that penetrates into the furnace from the furnace wall outer surface.

[0044]

EXAMPLE The furnace inner diameter was 800 mm and the furnace height was 5.5 m.
The present invention was implemented for a test blast furnace having three tuyeres at 20 degree intervals.

Table 3 shows the operating conditions at that time. In this test, sintered ore was used as an iron source material, and the blowing condition of the powdered carbon material, that is, the mounting position of the lance for blowing the powdered carbon material in the tuyere was determined by the combustion of the powdered carbon material. As in the case of the test using the test apparatus, cases 1 to 7 shown in Table 2 were used.

[0046]

[Table 3]

Evaluation of the blowing conditions of the pulverized carbonaceous material was performed by using the content sampler from the portion corresponding to the drip zone at the lower part of the furnace, and examining the content of fine particles passing through a 5 mm sieve in the coke in the furnace (coke powder). Rate).

FIG. 3 shows the results. As is clear from this figure, when the powdered carbonaceous material is blown by adjusting the position of the tip of the lance for blowing the carbonaceous material so as to satisfy the requirements specified in the present invention (cases 1, 2, 5 and 6), powdering of coke at the lower part of the furnace could be suppressed. This makes the powdered carbon material blown from the tuyere effectively act as a reducing agent,
This is because the reaction deterioration of coke could be suppressed.

[0049]

According to the blast furnace operating method of the present invention,
The powdered carbon material blown from the tuyere can be effectively used as a reducing agent without the need for new equipment, and it is possible to suppress the pulverization due to the reaction deterioration of coke and the deterioration of the air permeability in the furnace due to the deterioration. . Further, it is possible to relax restrictions on coke quality such as improvement in coke strength.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a pulverized carbonaceous material blowing section in a pulverized carbonaceous material combustion test apparatus, in which (a) is a plane including the tip of a powdery carbonaceous material blowing lance and the center axis of a tuyere; 4) is a view including the tip of the tuyere and projecting the tip of the lance perpendicular to the plane perpendicular to the center axis of the tuyere.

FIG. 2 is a view showing the test results obtained by a powdered carbonaceous material combustion test apparatus, showing the burning rate of the powdered carbonaceous material when the mounting position of the powdered carbonaceous material blowing lance in the tuyere is changed.

FIG. 3 is a view showing test results of a test blast furnace, showing the coke powder ratio of the powdered carbonaceous material when the mounting position of the powdered carbonaceous material injection lance in the tuyere is changed.

[Explanation of symbols]

 1: Tuyere 2: Lance for blowing carbonaceous material 2-1: Projection point at the tip of lance 3: Center axis of tuyere 4: Center of tuyere

Claims (1)

[Claims] 1. A powdery carbonaceous material is blown into a furnace together with a carrier gas by using a powdery carbonaceous material blowing lance mounted in the tuyere so as to satisfy the following conditions (1) to (3). A method of operating a blast furnace, characterized in that: (1) The projection point of the tip of the lance perpendicular to the plane including the tip of the tuyere and perpendicular to the center axis of the tuyere satisfies the following equation. 0.5 × R _t <R _b ··· However, R _t: tuyere radius R _b: a distance between the center axis of the center of the tuyere of the lance tip projected image. (2) In the plane described in (1), an angle θ formed with respect to a vertical upward direction (reference) of a straight line connecting the projection point of the tip of the lance and the center of the tuyere satisfies the following expression. −45 ° ≦ θ ≦ + 45 °… However, the angle is + clockwise and − counterclockwise with respect to the reference.
And (3) In a plane including the tip of the lance and the center axis of the tuyere, a straight line connecting the center of the tip of the lance and the upper tip of the tuyere is defined with respect to the tuyere forward direction (reference) of the center axis of the tuyere. The angle φ satisfies the following equation. 45 ° ≦ φ where the angle is an angle with respect to a reference when the tuyere front direction is set to the left in the plane.